1. Field of the Invention
The invention is related to the field of magnetic disk drive systems, and in particular, to recording heads of a magnetic disk drive system that include electrical pads on multiple surfaces.
2. Statement of the Problem
Many computer systems use magnetic disk drives for mass storage of information. Magnetic disk drives typically include one or more recording heads (sometimes referred to as sliders) that include read elements and write elements. A suspension arm holds the recording head above a magnetic disk. When the magnetic disk rotates, air generated by the rotation of the magnetic disk causes an air bearing surface (ABS) of the recording head to ride a particular height above the magnetic disk. The height depends on the shape of the ABS. As the recording head rides on the air bearing, an actuator moves an actuator arm that is connected to the suspension arm to position the read element and the write element over selected tracks of the magnetic disk.
To read data from the magnetic disk, transitions on a track of the magnetic disk create magnetic fields. As the read element passes over the transitions, the magnetic fields of the transitions modulate the resistance of the read element. The change in resistance of the read element is detected by passing a sense current through the read element and then measuring the change in voltage across the read element. The resulting signal is used to recover the data encoded on the track of the magnetic disk.
Recording heads are typically manufactured on a substrate wafer. Thin films are deposited on the substrate to create an array of recording heads on the wafer. The wafer is then cut into rows, and each row of recording heads is lapped. The rows are then cut into individual recording heads. The ABS of each individual recording head is then milled to a desired shape.
FIG. 1 illustrates a typical recording head 100. Recording head 100 includes a substrate portion 110 abutting a deposited portion 120. Deposited portion 120 comprises the portion of the recording head formed by depositing the thin films, and the substrate portion 110 comprises the wafer portion. A read element and a write element (not shown) are embedded in deposited portion 120. Electrical pads 142-143 are located on an end surface 122 of deposited portion 120. End surface 122 is perpendicular to an air bearing surface (ABS) 130 of recording head 100. ABS 130 is the bottom surface as recording head 100 sits on the page of FIG. 1. Electrical pads 142 connect to the write element through electrical connections (not shown) embedded in deposited portion 120. Electrical pads 143 connect to the read element through electrical connections (not shown) embedded in deposited portion 120. Electrical pads 142-143 provide a contact point to the read element and the write element.
Head designers are designing recording heads that have other electrical elements in addition to the read element and the write element. Some of the electrical elements are temporary and some are permanent. One example of a temporary electrical element is an electrical lapping guide used for controlling the depth of the lapping process. One example of a permanent electrical element is a heater. For each of these electrical elements that are added to a recording head, electrical pads are needed to provide a connection point for the elements. In FIG. 1, electrical pads for the additional electrical elements would be located on end surface 122 along with electrical pads 142-143. Thus, if a heater is included in recording head 100, then end surface 122 would include six electrical pads. If a heater and an electrical lapping guide are included in recording head 100, then end surface 122 would include eight electrical pads (assuming eight electrical pads would fit on end surface 122).
One problem facing head designers is having enough surface area on the end surface for the electrical pads needed for the electrical elements in the recording heads. As head designers add more electrical elements, more electrical pads need to be added. At the same time, the overall size of the recording heads is being reduced to implement smaller form factor disk drives. Due to the size of a typical recording head, a limited number of electrical pads (such as six or seven) can be included on the end surface of the recording head. Head designers unfortunately may desire to include more electrical elements than allowed by the limited number of electrical pads.